Systems for tracking persons, especially criminal offenders, parolees, subjects of restraining orders, and the like, have typically used two types of mechanisms for establishing the location of the person of interest. The first is a typical home arrest, house arrest, system as described by U.S. Pat. No. 5,523,740 issued Jun. 4, 1996 to Burgmann. This system uses a base station at a fixed location and connected to a phone line. The person of interest wears a portable transmitter or beacon that periodically transmits a radio frequency signal or ping. If the beacon is in range of the base station the base station detects this ping and records that the subject is at the location being monitored by the base station at that time. The base station can be programmed with rules requiring that the transmitter, and by implication the person of interest, be within range of the base station at particular times. If the base station is programmed to expect the person of interest to be within range, but does not detect the ping from the transmitter, the base station can then call the monitoring authority to report the violation of the rules.
A variation on this first system retains the beacon affixed to the person of interest, but allows for a mobile transmitter that has location detection circuitry, such as is described by U.S. Pat. No. 6,072,396 issued Jun. 6, 2000 to Gaukel. In both the cases described above, a beacon is fixed to the person of interest and the beacon sends out an intermittent signal which is detected by a base station. The base station may manage rules determining when the beacon is to be in range of the base station and report any violations to a monitoring authority.
In the second type of monitoring system, the person of interest is monitored at all times using an intelligent remote tracking device and the entire device used in the monitoring is securely attached to the person of interest. Examples of these types of systems are disclosed in United States Patent Application Nos. 2008/0018458, 2008/0018459, 2008/0012761 and 2008/0012760, the disclosures of which are hereby incorporated by reference. In this case there is no beacon required, as the device is regularly or continually monitoring for tampering and location and reports the location and status of the device to a monitoring center or monitoring authority. This second type of system is illustrated in FIG. 1, which shows the major elements of a remote tracking system. System 100 is used to track multiple intelligent remote tracing devices (RTDs). Each RTD 101 includes a positioning system engine, such as a global positioning system (GPS) engine, which is able to receive signals from one or more sources, either terrestrial networks or satellite network such as multiple GPS satellites 102, and to perform a location calculation based on the signals from the sources.
In addition to a GPS engine, the RTD includes a wireless/cellular transceiver. After a location determination has been made by the GPS engine or an internal microprocessor, the location information and information indicating the status of the RTD is sent over a terrestrial network, which is preferably a cellular network, as shown by cellular network 103, but can be any other type of communications network, including two way radio, satellite or other network. In order to be useful, each position location for the RTD needs to include an indication of the time for the location. In a preferred embodiment, the RTD uses the time information contained in the GPS signals themselves to provide the time indication for the position determination; however, instead of using the time information from the GPS signal, the RTD itself may provide the time indication from an internal clock. An internal clock may also be used to provide time indications on when data packets were created and sent using the cellular connection.
The information sent by the RTD over its cellular connection is received by monitoring center 104. Monitoring center 104 is preferably a staffed monitoring center providing representatives who can act as an intermediary between the person being monitored and the parole officer, supervisor or administrator with responsibility for the person being monitored. The monitoring center also includes the computer resources required to process, store and analyze the data received from the RTDs and provide the interface for the officers/supervisors/administrators to review the information in the system and to setup, modify and terminate the operating parameters for each individual RTD. Access to the information in the monitoring center is available through a web interface which connects to a network 105, such as the Internet, which allows persons with authorization 106 outside the monitoring center to access information in the monitoring centers computers.
While the second, wholly contained monitoring device and system, is more flexible and offers advantages over the first system and its reliance on base stations, the second type tracking device and system could benefit from fixed points of reference independent of the internal location detection mechanisms.